Referigerating apparatus



July 16, 1963 L. J. MANN ETAL REFRIGERATING APPARATUS Filed Oct. 24, 1960 2 Sheets-Sheet 1 B 58 0 a WHMO/ En.am v, aflm e NM! 0 1 W w J .C f 4! dA A r a r H00 .I w w/ M LWE T a m 7 July 16, 1963 J. MANN ET AL REFRIGERATING APPARATUS 2 Sheets-Sheet 2 Filed Oct. 24. 1960 IIIIIIII Inn-lull IIIIIIII IN VEN TORS Leonard J. Mann Vie for A. William/71's E dward C. 5 'mmons Their Attorney United States Patent 3,097,509 REFRIGERATHJG APPARATUS Leonard J. Mann, Victor A. Williarnitrs, and Edward C. Simmons, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Oct. 24, 1960, tier. No. 64,620 2 Claims. 3!. 62-469) This invention pertains to refrigerating apparatus and more particularly to means for adjusting the amount of active refrigerant in a refrigerating system accord ng to environment temperatures to maintain desired refr1gerating temperatures despite variations in room temperatures.

In the Wurtz et a1. Patent 2,672,020, issued March 1d, 1954, the oil in the oil reservoir of the compressor 1s relied upon to absorb and evolve refrigerant under cool and warm room temperature conditions to vary the amount of active refrigerant in the system to marntaln desirable refrigerator temperatures in both refrigerated compartments. It has been found that the amount of oil normally required for lubrication in such a system 18 not sufficient to absorb and evolve all of the refrigerant necessary to achieve the desired adjustment of the active refrigerant in the system to compensate for varying room temperatures. While it might be possible to enlarge the oil reservoir and provide a surplus of oil for this purpose, this is not completely desirable, since it is possible for this oil to migrate to the condenser and the evaporator of the refrigerating system and interfere with the proper operation of the system. Also, the large mass of this oil resists rapid changes in temperature due to changes in environment temperature and causes any adjustment of the amount of active refrigerant in the system to lag behind the changes in conditions.

It is an object of this invention to provide a refrigerating system with a simple inexpensive effective arrangement for withdrawing adequate amounts of the refrigerant from active circulation in the refrigerating system under cold environment or room conditions sufiicient to compensate the refrigerating system reduction and change in pattern of the heat leak of the refrigerator.

It is another object of this invention to provide between the compressor and condenser of a refrigerating system a compensating liquid refrigerant trap for removing in increasing amounts some refrigerant from active circulation as the room temperature falls.

Refrigerator manufacturers have been satisfied if their refrigerators operate satisfactorily between 70 F. and 110 F. However, refrigerators are required frequently to operate at temperatures below 70 F.

It is, therefore, another object of this invention to provide a refrigerator which will operate satisfactorily at temperatures below 70 F. as well as between 70 F. and 110 F.

These and other objects are attained in the forms shown in the drawings in which an insulated refrigerator cabinet is provided with below and above freezing compartments insulated from each other and each provided with a separate evaporator which are connected in series. Each evaporator is located outside the compartment to be cooled and air is circulated over each of the evaporators individually by a fan which draws the air from and returns the air to the compartment to be cooled. The compressor Withdraws the evaporated refrigerant from the evaporator associated with the warmer compartment through a suction conduit and compresses the refrigerant and first forwards the compressed refrigerant to a superheat removing coil which cools the refrigerant sufiiciently that when this refrigerant is returned to the compressor the oil therein is liquefied and removed from the refrigerant in the compressor to return to the oil reservoir while "ice the substantially lubricant-free refrigerant passes to-the. compressor outlet.

To obtain more desirable refrigerator temperatures in the compartments as the room temperature falls, it is desirable to starve the evaporator associated with the warmer compartment as the room temperature falls.- Although absorption of refrigerant in the oil in the oil reservoir tends to accomplish this to a limited extent, this alone is not adequate. In this invention this starving effect is considerably increased by providing an elongated upright liquid refrigerant trapping container which is clamped in heat transfer relation with the outer. metal structure of the refrigerator so that it is responsive to room temperature. The top of this container is con: nected to the top of the condenser while the bottom outlet of. the condenser is connected through a capillary refrigerant tube to the inlet of the evaporator associated with the below freezing compartment. A long discharge gas cooling conduit connects the outlet ofrthe compressor with an intermediate portion of the elongated upright container just below the midpoint thereof. This arrangement by condensing the compressor discharge vapors and fur: ther removing heat to produce subcooled liquid refrigerant causes the trapping of increasing amounts of liquid refrigerant in the bottom of the elongated container as the room temperature falls to starve the evaporator associated with the warmer compartment more and more as the amount of active refrigerant circulating within the system is reduced. The location of the connection between the compressor discharge gas cooling conduit and the container at or adjacent the midpoint of the container varies and limits the amount of refrigerant which is trapped in the container at low temperatures so that the system will function to produce desired refrigerating temperatures at room temperatures far below F. as well as temperatures as high as F.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings where in preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a vertical irregular sectional view taken along the line 1-1 of FIGURE 2 illustrating a refrigerating system embodying one form of my invention;

FIGURE 2 is a fragmentary vertical sectional view of a two-compartment refrigerator taken substantially along the line 2.2 of FIGURE 1;

FIGURE 3 is a fragmentary sectional view illustrating a modified form of the invention in which battles are provided within the elongated container; and

FIGURE 4 is a simplified wiring diagram.

Referring now to the drawings and more particularly to FIGURE 2, there is shown an insulated refrigerator cabinet containing an upper above-freezing compartment 20 and a lower below-freezing compartment 22 separated by an insulated dividing wall 24. Each of these compartments is provided with a separate insulated refrigerator door designated respectively 26 and 28. A first evaporator 30 of the fin and tube type is located beneath the false bottom wall 32 of the below-freezing compartment 22. Air is drawn from the below-freezing compartment 22 through the air inlet 34 provided at the front of the evaporator '30 by a centrifugal fan 36 driven by an electric motor 38 located in the rear wall of the cabinet. The duct work 40 conducts the flow of cooled air from the evaporator 30 through the inlet of the fan 36 and directs the discharge of the cooled air to the upper rear portion of the compartment 22. The false bottom wall may be used to support ice trays and packages to be kept at belowfreezing temperatures.

A second evaporator 42, in the form of a vertical refrigerator evaporator plate, is located behind the false rear wall 44 and tails the evaporator 30 in the refrigerant circuit. It includes the serpentine refrigerant passages 46 connected to the conduit 48 providing the connection between the outlet of the first evaporator 30 and the second evaporator 42. The serpentine refrigerant passes 46 connect with the bottom of the accumulator chamber 50. The top of this accumulator chamber 50 connects with the suction conduit 52, 49 connecting with the inlet of the high side sealed motor compressor unit 54 located in the machinery compartment beneath the bottom insulated wall 58 of the belowfreezing compartment 22. The rear wall of the above-freezing compartment 20 is provided with a centrifugal fan 60 driven by an electric motor 62 in the rear wall of the cabinet for drawing air from the above-freezing compartment 20 and circulating in heat transfer with the plate evaporator 42. As shown in the wiring diagram of FIGURE 4, the compressor motor which drives the compressor within the sealed unit 54 is connected in parallel circuit with the fan motor 38 and in series with the thermostatic switch 66 controlled by the temperature of the thermostat bulb 68 mounted on the upper portion of the plate evaporator 42. The fan motor 62 is connected directly in series with the thermostatic switch 70, not shown in FIGURE 2 but which is responsive to the temperature of the above-freezing compartment 20.

The suction conduit 49 connects with a combined compressor inlet and outlet connection 72 provided at the bottom of the sealed unit 54. The compressor within the sealed unit '54 compresses the refrigerant withdrawn through the suction conduit 52, 49 and forces the hot compressed refrigerant out through the connection 72 and the conduit 74 into the fin and tube superheat removal coil 76 located in the machinery compartment 56 in front of the bottom of the sealed unit 54. It is supported by a U-shaped rubber mounting upon the front sill of the machine compartment. The hot compressed refrigerant is cooled in the superheat removal coil '76 sufficiently that when it is returned through the conduit 80* to the interior of the sealed unit 54 that any lubnicant therein will be liquefied and separated from the refrigerant in the sealed unit 54 and returned to the oil reservoir therein.

It is known (Wurtz et al. 2,672,020, column 11, line 43 to column 14, line 56) that the quantity of refrigerant actively circulating within the refrigerating system is quite critical in obtaining a maximum efficiency and the desired refrigerating temperatures. Even in a single evaporator system it is known that better results are obtained when there are more active refrigerant circulating in the system under high temperatures and loads than is desirable at low temperatures and low loads. It is also known that this is more critical in restrictor types of systems than in systems provided with expansion vailves. In two compartment refrigerators having separate evaporators for each, further complications are entailed. For maintaining the temperature substantially constant in both the compartments regardless of environment temperatures, the refrigerating requirements for the higher temperature compartment increase much faster than the refrigerating requirements for the low temperature compartments. In the aforesaid Patent 2,672,020, the absorption and evolution of the refrigerant into and out of the oil is relied upon to adjust the quantity of refrigerant in active circulation. The oil in the oil reservoir of the sealed unit 54 does absorb and evolve refrigerant but we find that the amount is insuflicient.

According to our invention, this withdrawal and return of refrigerant from and to active circulation is accomplished by a liquid trapping system between the outlet 82 of the sealed motor compressor unit 54 and the inlet of the condenser 84. The condenser 84 consists of a serpentine tube mounted upon a perforated metal sheet 86 having side flanges 88 and 90 which are fastened to the sheet metal outer wall 123 of the refrigerator. The

side flanges 88 and are also fastened to a rear metal plate 92 forming the back of the machinery compartment 56 and having a large central opening '94 therein. This plate 92 is likewise fastened to the outer metal shell 123 of the refrigerator cabinet and is in direct thermal exchange relation therewith so that it is directly responsive to the room or environmental temperature thereof.

The liquid refrigerant trap includes an elongated upright container 96 of 1% inch copper tubing about ten inches long which is closed at its lower end and has an entrance inlet 98 about five and one half inches down from the top. The distance the inlet 98 is below the top of the container 96 is critical for any given diameter thereof; however, this is affected by the length of the tubing between the outlet 82 and the inlet 98. For the system shown, this distance from the top should be at least five and one half inches. For cooling the gas discharged from the outlet 82, the inch copper tubing 121 extends upwardly between the condenser 84 and the rear outer sheet metal wall 123 of the cabinet. The length of this tubing is also rather critical. For a thirteen cubic foot refrigerator of the design shown containing twenty ounces of refrigerant and fifteen ounces of oil, this length should be about six feet, whereas for a fifteen cubic foot refrigerator, this length should be about eight feet. The container 96 is clamped by a band clamp 125 extending substantially throughout its length to the rear closing wall 92 of the machinery compartment 56. This rear closing Wall 92 is provided with flanges 127 which are clamped to the rear of the outer sheet metal shell 123 of the cabinet so that heat is dissipated throughout this large sheet metal surface so that through this heat transfer arrangement the container 96 is being maintained substantially at room temperature at all times. This is important since the faster the heat is withdrawn from the container 96 the more liquid is stored in the bottom thereof. Also, the higher the inlet 98 above the bottom, the more liquid is stored. Also, the longer the section of tubing 121 is, the more liquid is stored in the container 96. These factors should be varied according to the heat balance characteristics of the design, such as the effectiveness of the insulation, the amount of absorption of the refrigerant in the lubricant, the amount of refrigerant charge, the volume of the accumulators and evaporators and the characteristics of the restrictor to provide the amount of compensation desired. In a 70 F. room at the end of a typical running cycle, the bottom of the container 96 is maintained at a temperature of about 90 F. The refrigerant (Freon 12) leaves the compressor outlet 82 with about 35 superheat (142 F.) and is cooled in the tube 121 to about a 3 or 4 F. superheat (110 F.). The cooling in the container is sufiicient to cool to a temperature of about F. some of the vapor along the walls of the container 96 below the saturation point (107 F.) of the refrigerant causing some to condense by removing the heat of condensation for flow down the walls of the container 96 and then subcooling the condensed refrigerant in the bottom of the container 96 to the temperature of about 90 F. The top of the container 96 is connected by the conduit 129 to the top of the condenser tubing 84. The bottom of the condenser tubing 84 is conneoted to the filter-drier 131 which connects through the capillary tubing 133 extending alongside the section conduit which connects with the tube 135 extending to the inlet of the evaporator 30.

When this system operates at room temperature, such as F., substantially no refrigerant collects or is retained in the container 96. The system therefore has the maximum amount of refrigerant in active circulation through the system which raises the back pressure to make the system operate at greatest efficiency. The tube 121 adds condensing capacity to the system to improve its efficiency. As the room temperature lowers, more and more refrigerant collects in the bottom of the container 96, thereby reducing the amount of active refrigerant circulating through the system in proportion to the lowering of the room temperature. This makes it possible for the refrigerator to maintain proper temperatures in both compartments from 110 down far below 70 F. The location of the inlet 98 adjacent the midpoint of the container 96 by the upward circulation of compressed refrigerant prevents the collection of excessive amounts of liquid refrigerant at colder room temperatures. It also acts to maintain the proper relationship between the temperatures of the two compartments 20 and 22 by reason of the fact that when more refrigerant actively circulates in the system there is proportionately more liquid refrigerant in the second evaporator 42 so that more refrigeration in proportion is provided for the compartment 20 so that a greater proportion of cooling is provided for this compartment as is required when the room temperature is high.

A relatively sudden demand for greater refrigeration also puts more liquid refrigerant into active circulation in the system. For example, should ice trays filled with water he placed upon the false bottom wall 32 causing an increased evaporation of refrigerant in the system and Warming both evaporators, the motor compressor unit will operate for longer periods of time. This would provide a longer period of circulation of gases through the upper portion of the container 96 and these gases would be at a higher temperature to carry more refrigerant away from the container 96 and remove a considerable portion of the liquid stored therein and place it into active circulation in the system. This, of course, raises the back pressure of the system and makes it possible for the system to more rapidly supply refrigeration primarily to the first evaporator '30 and secondarily to the second evaporator 42. Therefore, the system will be quickly adjusted to bring the temperatures to their normal values despite the relatively sudden imposition of the heavy load. This will also be true if the heavy load is applied in the compartment 20.

The liquid refrigerant trapping system also reduces ofi? cycle losses. Particularly, it reduces during the off cycle the flow of warm liquid refrigerant flowing from the condenser into the evaporator 30. The liquid delivered to the evaporator 30 during the off cycle is reduced by the amount of liquid refrigerant which condenses during the off cycle in the container 96 and the tubing 121. Because the liquid trapping system reduces the volume of liquid refrigerant in active circulation to the system at colder room temperatures, it substantially prevents liquid refrigerant from entering the suction conduit 52, 49 and causing frosting of this conduit. By preventing this, it also tends to prevent variations in the volume of the two evaporators from causing poor refrigeration or damage to the compressor and reduces the amount of space required in the accumulator 50.

While this liquid trapping system is especially advantageous for the two-evaporator, two-compartment refrigerator, as illustrated herein, it also has advantages in a single evaporator system particularly in that the size of the accumulator chamber can be reduced in such a system.

If desired, baffles, such as the bafiles 137 shown in FIGURE 3 having openings on opposite sides thereof to provide a tortuous refrigerant flow, can be provided in the upper portion of the container 96. Use of such baffies 137 will reduce the necessary length of the upper portion of the container 96. Also, if desired, the container 96 may be provided with an adsorbent, such as silica gel or activated alumina; however, because of its simplicity and lower cost, we prefer to use a container 96 without baffles and without any adsorbent.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

:1. Refrigerating apparatus containing a refrigerant and a lubricant including evaporating means, a compressor means having a suction inlet connected to said evaporating means and having an outlet, means associated with said outlet for removing lubricant from the compressed refrigerant and returning the removed lubricant to the compressor means, a condenser, a capillary tube restrictor means connecting said condenser and evaporating means, a liquid refrigerant trap for trapping increasing amounts of liquid refrigerant as the environment temperature of the compressor means falls comprising a container elongated in the ascending direction having its upper portion connected to said condenser, and heat dissipating conduit means of substantial length connecting the outlet of said compressor means with a portion of the interior of said container adjacent the region midway between the top and bottom thereof.

2. Refrigerating apparatus including an insulated cabinet provided with an outer rnetal shell and two insulated chambers within the shell, a refrigerating system containing a refrigerant and a lubricant including evaporating means having two sections connected in series, one of said sections being associated in heat transfer relation with each of said chambers, a compressor means having a suction inlet connected to said evaporating means and having an outlet, means associated with said outlet for removing lubricant from the compressed refrigerant and returning the removed lubricant to the compressor means, a condenser, a capillary tube restrictor means connecting said condenser and evaporating means, a liquid refrigerant trap in heat transfer relation with said outer metal shell for trapping increasing amounts of liquid refrigerant as the environment temperature of the compressor means falls comprising a container elongated in the ascending direction having its upper portion connected to said condenser, and heat dissipating conduit means of substantial length connecting the outlet of said compressor means with a portion of the interior of said. container substantially midway between the top and bottom thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,155,051 Kagi Apr. 18, 1939 2,359,595 Urban Oct. 3, 1944 2,433,187 Alsing Dec. 23, 1947 2,433,188 Kalischer Dec. 23, 1947 2,749,723 Webber June 12, 1956 2,954,681 McCorrnack Oct. 4, 1960 3,009,335 Alsing Nov. 21, 1961 FOREIGN PATENTS 833,360 France July 18, 1938 

2. REFRIGERATING APPARATUS INCLUDING AN INSULATED CABINET PROVIDED WITH AN OUTER METAL SHELL AND TWO INSULATED CHAMBER WITHIN THE SHELL, A REFRIGERATION SYSTEM CONTAINING A REFRIGERANT AND A LUBRICANT INCLUDING EVAPORATING MEANS HAVING TWO SECTIONS CONNECTED IN SERIES, ONE OF SAID SECTIONS BEING ASSOCIATED IN HEAT TRANSFER RELATION WITH EACH OF SAID CHAMBERS, A COMPRESSOR MEANS HAVING A SUCTION INLET CONNECTED TO SAID EVAPORATING MEANS AND HAVING AN OUTLET, MEANS ASSOCIATED WITH SAID OUTLET FOR REMOVING LUBRICANT FROM THE COMPRESSED REFRIGERANT AND RETURNING THE REMOVED LUBRICANT TO THE COMPRESSOR MEANS , A CONDENSER, A CAPILLARY TUBE RESTRICTOR MEANS CONNECTING SAID CONDENSER AND EVAPORATING MEANS, A LIQUID REFRIGERANT TRAP IN HEAT TRANSFER RELATION WITH SAID OUTER METAL SHELL FOR TRAPPING INCREASING AMOUNTS OF LIQUID REFRIGERANT THE ENVIRONMENT TEMPERATURE OF THE COMPRESSOR MEANS FALLS COMPRISING A CONTAINER ENLONGATED IN THE ASCENDING DIRECTION HAVING ITS UPPER PORTION CONNECTED TO SAID CONDENSER, AND HEAT DISSIPATING CONDUIT MEANS OF SUBSTANTIAL LENGTH CONNECTING THE OUTLET OF SAID COMPRESSOR MEANS WITH A PORTION OF THE INTERIOR OF SAID CONTAINER SUBSTANTIALLY MIDWAY BETWEEN THE TOP AND BOTTOM THEREOF. 